Borehole drilling system



April 1965 J. M. KELLNER ETAL 3,180,436

BQREHOLE DRILLING SYSTEM 2 Sheets-Sheet 1 Filed May 1, 1961 mes E. Reedv exonder B. Hildebrand? INVENTORS r e n H K M n 0 5 k C O J I Iii-vATTORNEY Alexander B. HildebrondiiNVEA/TORS April 27, 1965 Filed May 1,1961 (Mfl 5. M

ATTORNEY United States Patent 3,186,436 BOREHOLE DRHJLING SYSTEM JacksonM. Kellner, James E. Reed, and Alexander Hildebrandt, all of Tulsa,Girls, assignors to .iersey Production Research fiompany, a corporationof Delaware Filed May 1, 1961, Ser. No. 106,597 15 Claims. (Cl. 175-57)The present invention relates to the drilling of wells and similarboreholes and more particularly relates to an improved system for theapplication of force to a bit during the drilling of such boreholes. Instill greater particularity, the invention relates to a method andapparatus for continually urging a drill bit against the bottom of aborehole by the application of upward force against the borehole wall.

Systems currently in use for the drilling of wells and similar boreholesrequire that a string of drill pipe and a rotary or percussive drill bitbe suspended in the borehole by means of a suitable drilling rig. Thepipe and bit are generally rotated in the hole by a rotary table on therig floor while drilling fluid is circulated through the pipe andsurrounding annulus by pumps or compressors in order to cool the bit,prevent the entry of fluids into the hole, and carry cuttings to thesurface. In such systems, the force applied to the formation at thebottom of the hole by the bit is controlled by means of heavy drillcollars connected between the drill pipe and the drill bit. These drillcollars are generally several hundred feet in length and may weigh fiftythousand pounds or more. The collars concentrate the weight used for theapplication of force to the bit near the lower end of the drill stringand thus permit the relatively thin-walled drill pipe above them to beheld in tension. This cuts down flexing and buckling of the pipe as thedrill string is rotated, reducing the likelihood of drill string failureand minimizing the tendency of the bit to deviate from the desireddirection.

Although drill collars are widely employed in the manner describedabove, their use is accompanied by certain disadvantages. A much largerdrilling rig is required where a heavy column of drill collars is usedthan would be necessary if the collars did not have to be raised duringtrips into and out of the hole. The time and energy required to handlethe collars are significant factors in determining total drilling costs.Sticking of the drill string in the borehole is often attributable tothe presence of the collars. The length of the collars frequentlyprevents their use in drilling through hard formations lying very closeto the earths surface. These and other disadvantages will be be familiarto those skilled in the art.

Accordingly, it is an object of this invention to provide an improvedmethod for the continuous application of force to the bit during thedrilling of wells and similar boreholes which will obviate the necessityfor utilizing conventional drill collars.

It is another object of this invention to provide a method and apparatusfor continuously urging a bit downwardly against the formation at thebottom of a borehole by the application of force against the boreholewall.

These and objects which will be obvious from the accompanying disclosureare attained in accordance with the invention by continually applyingupward force to the borehole wall at successively lower points from alimited section of the drill string located near the bit. By thus urgingthe drill string downwardly at a rate equal to or in excess of that atwhich the bit advances, the force required for satisfactory drillingrates can be applied to the bit continuously without the necessity foremploying conventional drill collars. The resulting reduction in theweight of the downhole equipment permits the use of a smaller drillingrig and power source and reduces the cost of handling the string duringtrips into and out of the borehole. Difliculties due to sticking of thestring in the hole are mitigated. Problems in drilling through hard,very shallow formations are largely avoided. The net results is thus anover-all increase in drilling eiiiciency.

Several diiferent forms of apparatus may be utilized in practicing themethod of the invention. A preferred form includes a tubular shaftinsertable in the lower part of the drill string through which fluid maybe circulated to the bit and an outer sleeve surrounding the shaft in asealing, rotatable relationship. A thrust bearing or similar means isprovided to prevent or restrict longitudinal movement between the sleeveand shaft. Thrust membars are mounted in the wall of the sleeve and aredesigned to engage the wall of the borehole and exert an upward forceagainst it. The reaction is a downward force against the sleeve of theapparatus. This downward force is transmitted through the thrust bearingto to the shaft, thus forcing the bit connected to the shaft downwardlyagainst the bottom of the borehole. As will be seen from the ensuingdescription, thrust members of various types may be utilized to apply adownward force on the bit by applying upward force against the boreholewall.

The method of the invention and the apparatus utilized in conjunctiontherewith can best be understood by referring to the followingdescription and the accompanying drawing, in which:

FIGURE 1 is a vertical elevation, partially in section, illustrating apreferred embodiment of apparatus useful in practicing the invention;

FIGURE 2 is a cross-section taken along the line 22 of FIGURE 1;

FIGURE 3 is a schematic drawing showing a portion of the sealing latticein the apparatus of FIGURE 1;

FIGURE 4 shows an alternate thrust member arrangement for the apparatusof FIGURE 1; and

FIGURE 5 illustrates another embodiment of apparatus which may beemployed in the practice of the invention.

FIGURE 1 of the drawing illustrates the best mode presently contemplatedfor carrying out the invention. Depicted therein, suspended in borehole16, is a string of drill pipe 12 to which a tubular shaft or arbor 14 isconnected by suitable threads or other means. The arbor includes lateralports and connecting conduits which will be discussed hereinafter.Attached to the lower end of arbor 14 is an adapter 16 which in turn isconnected a bit 18. The arbor and adapter serve to convey drilling fluidfrom the drill pipe to the bit. The bit can be a conventional drag bitas shown or other rotary drilling tool, or it may instead be apercussion bit assembly including means for reciprocating the cuttingelements in response to fluid flow or rotation of the drill string. Thebit includes nozzles 26, only one of which appears in the drawing; Dueto the pressure drop across the nozzles, the pressure within the arboris considerably greater than the pressure in the annulus surrounding thetool.

Mounted about arbor 14 is a tubular sleeve or housing 22. Housing 22 asshown is rotatably supported about arbor 14 by upper thrust and radicalbearings 24 and lower thrust and radial bearings 26. The bearings,depicted in simplified form, reduce friction between the arbor andhousing and at the time prevent axial movement of the arbor with respectto the housing. Any downward force exerted on housing 22 is thereforetransferred through bearings 24 and 26 to arbor section 14.

Housing 22 contains a plurality of ports 28 extending through thehousing wall. These ports are spaced at intervals about the housing andare grouped in two or more vertically spaced rows. As shown in FIGURES 1and 2, there are two ports in the upper row spaced apart The ports inthe second row are likewise 180 apart but are rotated 90 with respect tothe ports tive port by an elastic collar 32 which is bonded to the V 7piston and surrounding wall ofthe port.

The elastic in the upper collars are made of rubber or similar materialimperrneable to fluids to permit extension of the pistons within theports in response to a difference in pressure across the wall of thehousing.

Each of the pistons mounted in the housing has an outer, upwardly-facingsurface 36 upon which is retained a slidably mounted thrust director orwedge 34. The downwardly facing inner surfaces of the wedges and theupwardlyfacing outer surfaces of the pistons, as illustrated, areinter-connected in a slidable relationship. Each upwardly- :facingsurface 36 contains a groove 40 within which spline 42 on downwardlyfacing surface 38 of wedge 34 is slidably fitted. To prevent wedge 34from sliding off surface 36 of piston 30 each piston is provided with aretaining groove 44 into which retaining tongue 46 extends downwardlyfrom spline 42. Retaining tongue 46 stops the downward movement of wedge34 when the retaining tongue contacts shoulder 48 at thelower end ofretaining groove 44.

Each Wedge 34 is provided with an upwardly extending resetting arm 50.As can be seen from the drawing, re-

setting arm 54) of wedge 34 contacts the outer surface of chamberadjacent one thrust'unit in each of the lower rows communicates with theannulus so that the corresponding pistons are retracted; while thatadjacent the other thrust unit in each row communicates with theinterior of arbor 14 so that the corresponding pistons are extendedoutwardly. In order to simplify the drawing,

all of the pressure ports and pressure relief passageways in the arborsection associated with the various thrust members are not shown. Itwill be obvious from the drawing, however, that the pressure chamberassociated with each thrust unit communicates with the interior of thearbor l for one-half of each revolution of the arbor section and for theother half of each revolution comhousing 22 as piston 30 moves 'into'itsretracted position and in effect forces wedge 34 downwardly on the outersurface 36 of the piston. For convenience, each port and thecorresponding piston, wedge and collar will be referred to as a thrustunit. Thus the drawing shows twelve thrust units arranged in six rows,each row containing two thrust units which are spaced 180 apart. Thethrust units are identified on the drawing by reference numerals 60Athrough 60].

A sealing lattice is positioned between the exterior of arbor section 14and the internal bore of housing 22/ A lattice-type seal which can bemade of rubber or similar resilient material is illustrated in FIGURE 3.As shown, this seal comprises seven annular sections, 52A through 526,which are interconnected by elongated upright sections 54. Adjacentvertically-spaced upright sections are rotated 90 with respect to eachother. Upright sections between adjacent annular sections are spaced 180apart.- Upper annular section 52A fits in an annular groove in the innerhoning wall above the uppermost row of ports in housing 22. Lowerannular section 526 fits in a sim 'ilar groove in the inner housing wallbelow the bottom row of ports in the housing. Intermediate sections 52Dsimilarly provided forthe upright sections of the seal. The inner spacebetween arbor section 14. and the interior bore of housing 22 is thusdivided by the sealing lattice shown in FIGURE 3 into twelve pressurechambers, there being one such chamber for each thrust unit.

municates with the annulus 58. 'The conduit and port arrangement ofarbor 14 as shown is such that each thrust When the pressure chambercommunicates with the interior 56 of arbor section 14, the fluidpressure is greater than that in the annulusand the piston 30 is drivenout- It will be recognized that the arrangement of the thrust units, thepressure ports, and the pressure relief ports of the tool may bemodified from that shown in FIGURES 1 through 4 .of the drawing. Forexample, in lieu of providing two thrust units in each row as shown,three or more such units may be located: in, each row. The units inadjacent vertically spaced rows may be oifset from one another to attainsmoother operation and better lateral stability. Further, the pressureports and pressure relief ports in the arbor may be staggered. Thus itis seen'that various suitable arrangements of the 'thrust'units can beeffected as desired to obtain optimum performance.

In the operation of the apparatus shown in FIGURES 1, 2 and 3, drillingfluid under pressure is circulated down- ,wardly through drill string12, through interior 56 of 'shown in FIGURES land 2, thrust units MA,690, 60E,

andfitlG and 60] are retracted because the corresponding pressurechambers are open to annulus 58 at a lower pressure than that withinthe" drill string. The pressure in the annulus 58 is usually 600 to 1000psi. or more "below that" in the drill" string. When the pressure isequalized across" the resilient seal of piston 30, the elastic through52F fit in annular grooves in the housing wall spaced vertically betweenthe rows of ports. Grooves are with thrust unit 69A communicates,through pressure relief passageway 62 with the annulus Stif The pistonof thrust unit 66A in the upper row is therefore retracted in- 'wardly..The pressure chamberassociated with thrust unit 60B communicatesthrough pressure port or passageway 64 with theinterio-r of arborsection 14, as shown in FIGURE 2 of the drawing. As a result, the pistonor thrust unit 6013 is extended outwardly} The pressure 'to improvetheir holding ability.

seal pulls the piston inwardly into its retracted position. As thepiston moves inwardly, the resetting arm 50 of -wedge 34 contacts theouter surface of housing 22 and I limits movement of the wedge.

'rnent of the piston results in the wedge being moved down- Furtherinward movewardly with a sliding action between surfaces 36 and 38. Thethrust wedge is thus moved downwardly with respect to the piston VThrust units 6613, 6013, 6ttFand60H as shown are extended outwardly.This is becausethe corresponding pressure'chambers are in. fluidcommunication with the against the formation borehole. The outer facesof the wedges which contact the borehole wall may be serrated Afterawedge comes into contact with the borehole wall as described above,further outward movement of the corresponding piston tends to force thewedge'upwardly. .Since'the Qouter surface of the wedge, is anchor'edagainst .the'wall' and c'annotmove upwardly, a downward' reaction forceis transferred to housing 22. Housing 22 moves downwardly in response tothis force. As it moves, the pistons move outwardly and downwardly withrespect to corresponding wedges. The downward thrust exerted againsthousing 22 is transferred through thrust bearings 24 and 26 to arborsection 14. The arbor section thus tends to move downwardly and henceforce the bit against the bottom of the borehole. Continued rotation ofarbor section 14 aligns pressure port 64 with the pressure chamberassociated with thrust unit 60A. Discharge conduit 62 is similarlyaligned with the pressure chamber associated with thrust unit tlB. Whenthis occurs, thrust unit 60A is actuated to engage the borehole wall andthrust unit 608 is retracted. The other thrust members are alternatelyactuated and retracted in similar manner as the corresponding pressurechambers alternately communicate with annulus 58 and the interior 56 ofarbor 14. The apparatus shown in FIGURES l and 2 thus permits theapplication of upward force to the borehole wall and downward force tothe bit.

FIGURE 4 of the drawing shows an alternate arrangement of the thrustunits on the apparatus described above. Piston or ram member 70 is setin radial port 72 of housing 22 and is held there by resilient sealingmeans 74 at an angle of approximately 45 above the horizontal plane.When extended, piston 70 contacts the borehole wall and tends to forcehousing 22 downwardly. This downward force is transmitted through thrustmeans 24 and 26 to arbor 14, thus forcing bit 18 downwardly against thebottom of the borehole. Alternate pistons 70 are retracted and reset inmuch the same manner as in the embodiment described above in connectionwith PIG- URES 1 and 2. The angle on which the center line orlongitudinal axis of piston 70 makes with the horizontal is usually inthe range of from about 30 to about 60". An angle of about 45 ispreferred, since such an angle permits a relatively long piston strokewithout requiring excessive space in the housing to accommodate thepiston and related members.

The amount of downward force applied against the drill bit in theapparatus described above in conjunction with FIGURES l and 2 of thedrawing depends on several factors. Assuming a pressure drop through thebit of 600 p.s.i., 60 1% inch diameter pistons of which 30 are active atone time and a thrust unit wedge angle of 45, 30,000 pounds downwardthrust can be generated. By doubling the pressure drop through the bitto 1200 psi, compatible with present practice, a downward thrust ofabout 60,000 pounds can be obtained. The amount of thrust can beincreased or decreased as desired, of course, by varying the pressuredrop across the bit, by varying the size of the thrust units, or byincreasing or decreasing the number of such thrust units.

It will be obvious from the foregoing that the downward force obtainedfrom the tool of the invention depends in part upon the length of thetool and the number of thrust units provided. In most cases the toolwill be designed to provide the maximum amount of force likely to beneeded. Where greater force than can be obtained by means of a tool ofgiven size is required, two or more tools may be used in tandem.

In utilizing the tool of the invention, the drill pipe above the toolwill normally be held in tension in order to prevent buckling and unduewear of the tool joints. In cases where it is desired to apply lessforce to the bit than is normally furnished by the tool, the tension inthe drill string can be increased by applying upward force to the drillstring at the surface with the rig equipment to lessen the effectiveforce of the bit. One instance where it is frequently desirable to dothis is in reaming operations. The ability to control the force appliedto to the bit in this manner is a particular advantage of the tool ofthe invention. Reduction of force on the bit is accomplished without areduction of the flow rate of the drilling iiuid. A reduction in thequantity of fluid circulated reduces the fluid available for cooling andlubricating the bit and lifting cuttings from the borehole and istherefore to be avoided. The use of an arbor which extends through thetool and rigidly connects the drill string and bit as disclosed hereinreadily permits control of the force on the bit.

FIGURE 5 of the drawing illustrates still another embodiment of theinvention. Shown in FIGURE 5, suspended in borehole 80, is a string ofdrill pipe 82.. Attached to the lower end of the drill pipe is arborsection 84 containing axial passageway 36 for the circulation of fluidthrough the tool. The arbor section is connected at its lower end todrill bit 88. Mounted about arbor section 84 is tubular housing 90. Thehousing is free to rotate and move axially to the arbor. Upper and lowersealing rings 92 and 94 respectively are set in grooves in the innerwall of the housing above and below annular chamber 96 between the outerwall of the arbor section and the inner wall of housing 90. Positionedwithin chamber 96 is an annular piston 98 which is affixed to orconstructed as an integral part of arbor section 84. Ring 100 in theouter face of the piston 98 provides a seal against the inner wall ofhousing 90. Chamber is thus divided into an upper or power section 102and a lower or discharge section 104. Upper section 102 communicateswith passageway 86 in the arbor section through port 106. Lower section104 communicates with annulus 108 outside the tool through port 110. Aprojection 115, having shoulder 113, is provided on the inner wall ofhousing N) to limit the downward movement of housing 90 with respect toarbor section 84.

A plurality of ports 111 extend through the wall of housing 90 intopower section 102 above piston 98. The ports are spaced at regularintervals about the housing and may be arranged in one or morevertically-spaced rows. An extensible shoe 112 is mounted in each portby means of an elastic collar 114 of rubber or similar fluid-imperviousmaterial bonded to the shoe and the surrounding wall of the port. Theouter surface of each shoe is provided with one or more curved runnersor skate elements 116 which extend across the shoe at an angle to thetransverse axis ,of the tool. The runners are preferably made oftungsten carbide or similar abrasion-resistant material. They may bewelded or otherwise affixed to the shoe surface or may instead beconstructed as an integral part of the shoe. When the shoes are extended, the runners contact the borehole wall. Rotation of the toolcauses the runners to move down the wall along spiral paths. It ispreferred that the runners on the various shoes be set to track the samegrooves cut in the borehole wall. The pitch at which the runners are setwill depend largely upon the speed at which the tool is to be rotatedand the rate at which the bit can be expected to advance. In general, itis preferred that the runners be set at an angle of from about 1 toabout 5 to the horizontal. A series of replaceable runners havingvarious pitch angles may be provided.

A clutch arrangement in the apparatus provides for the transfer ofrotary motion from the arbor section to the housing. The upper end ofarbor section 84 above housing 90 is enlarged to form shoulder 118.Mounted on the lower surface of the shoulder is an annular frictionplate 120 which may be made of tungsten carbide or similarabrasion-resistant material. The upper end of housing 90 is providedwith an annular friction plate 122 of tungsten carbide or the like whichmates with friction plate 120 to form a friction clutch.

In operating the tool shown in FIGURE 5, a drill string containing thetool is lowered to the bottom of the well bore. A gaseous or liquiddrilling fluid under pressure is then circulated downwardly througharbor 84 to hit 88 and is returned to the surface-through the annulus10%. The pressure in the annulus is considerably less than that withinthe tool because of the pressure drop acrossthe bit. Since upper chambersection 102 is connected with V the bit continuously.

i J 3. Apparatus for use I ,rotary bit which comprises in combination:

7 passageway 86 through port 196, the pressure in the chamber abovepiston 98 is also greater than that in the annulus.

hole wall. Before the runners 116 are securely anchored to the wall ofthe borehole, housing 9dmoves upwardly until plate 122 comes intocontact with plate 120 on the the borehole wall through the runners andhence no'axial force normally need be applied to the drill string at thesurface. string, arbor 84 and bit 88 from the surface.

or torque from the arbor to housing 99. The housing therefore rotates.

ilar to that in which. a tap advances as a hole is threaded. The rate atwhich the housing moves depends-upon the rate at which the bit advancesand the friction between the clutch plates. If the bit encountersrelatively soft strata and therefore tends to advance rapidly, the bitand I arbor Will -move downwardly relative to the housing. Thisincreases the friction between the plates, causing the housing to rotateand move downwardly more 'rapidly.

If the bit encounters hard strata and the drilling rate'decreases, thefriction between the plates will decrease.

There will be a corresponding decrease in the rate at which the housingrotates and moves downwardly. The

anchoring section of'the tool is thus continually advanced as drillingprogresses and hence a downward axial force, supplied by pressurefromthe drilling fluid, is applied to What is claimedis: 1. Apparatusfor use in drilling a borehole which comprises in combination:

a hollow rigid arbor section insertable in a string of drill pipe; ahousing member surrounding said arbor section in a scalable, rotatable,non-longitudinally movable a housing surrounding saidarbor'section in asealing,

rotatable relationship;

thrust means in said housing operable to engage the wall of saidborehole and exert a downward thrust V on said housing; 7 a

a and thrust transfer means to" transfer the downward thrust thusexerted on the housing'to said arbor section.

an arbor section connectable to the bit; l

a housing member surrounding said arbor section in a sealing,rotating-relationship;.

' thrust bearings interconnecting said housing member 1 Vand'said'arborsection; f

V a plurality of ports extending'throughsaid thousing member; r 7 r i aram member havinganoutwardly and upwardly facin each of said ports;

The fluid in section 192 tends to force piston. 98 downwardly andhousing 90- upwardly It also moves shoes 112 outwardly so thatrunnersl-lti contact the bore- Drilling is commenced by rotatingtheldrill 7 Friction betweenclutch plates 120 and 122 results in thetransfer Rotation of housing 90 causes runners 116 to advance down theborehole wall in a manner simindrilling a borehole using a ing surface,said ram member, being resilientlysealed 1 and conduit valve meanswithin said arbor section to alternately connect the inner side of saidresiliently sealed ram member with the interior of said arbor sectionand with the exterior of said housing as the arbor seetion is rotated.

4. Apparatus for use in drilling boreholes in the earth with a string ofdrill pipe and a bit which comprises in combination: 1 f

an arbor section .insertable in said drill string near said bit toestablish fluid communication between the drill string and bit;

a housing member surrounding said arbor section in a sealing androtatable relationship therewith, the in- .ner diameter of said housingmember being sufiirciently larger than 'the outer diameter of said arborsection to define an annular chamber between sa d arbor section. andhousing member;

an annular piston mounted in said chamber, said piston being attached tosaid arbor'section;

' port means in the lower portion of said housing for establishing fluidcommunication between saidchamber below said piston and the. exterior ofsaid housmg; Y

:port means in the wall of said arbor section above said piston .forestablishing fluid communication between V the interior of said arborsection and said chamber 7 above said piston; shoe members resilientlymounted'in ports in the wall of said housing member; 7 skate elementsmounted on the exterior surface of each of said shoes; 4 I an annulartraction plate surrounding said arbor'sfiction on the upper end of saidhousing; and a second, complementary friction plate .on sa d arborsection above said annular friction .plate for engaging said annularplate. 5. Apparatus as defined byclaim 4 wherein said skate elementshave a pitch of not over 5 degrees.

6. A method for drilling a borehole in the earth which comprises: 7 e srotating a drill bit at the end of a drill string insaid borehole whilecirculating a drilling fluid into the hole throughsaid drill string andbit; applying upward force to the borehole wall from a limitedsectioniof the drill string abovethebit in response to drilling fluidpressure within said drill string; V i V and thereafter applying upwardforce to the borehole wall at successively lower points on the wall at arate 5 I sufficientto maintain a continuous axial :force on saidbiti V7. A method asdefined; by claim 6 wherein upward points along'pat-hsparallel. to the axis of sa'idiborehole.

6 8. A method as defined by claim 16 wherein lupward io'rce isapplied tosaid borehole wall at successively lower points along spiral paths .onthe borehole wall;

' 9. Ina drilling method wherein a drilling fluid is circulated througha drill string suspended in a borehole and a cutting tool is conne'ctedatthe lower end of th V 7 string, the-improvementwhich comprises:

rotating said cuttingtool at the'lower end of said drill string; 7 T Vapplying upward force'tothe borehole/wall at spaced :points fromalimitedsection of the drill string 10- cated a fixed distance above saidcutting'to'ol in rewithinjs aidrdrill string; s

' torce is applied to said borehole Wall at successively lower sponse tofluid pressure exerted bysaid drilling fluid and the-reafter maintaininga continuous axial'force'on said cutting tool by applying force to saidborehole Wall at successively lower points on said wall as sa d boreholeis advanced.

10. A method as defined by claim 9 wherein said upward force is appliedto said borehole wall at successively lower points on the Wall alongpaths on the wall parallel to the axis of said borehole.

11. A method as defined by claim 9 wherein said upward force is appliedto said borehole wall as successively lower points along spiral paths onsaid wall.

12. Apparatus attachable to the lower end of a string of drill pipe forforcing a bit against the bottom of a borehole comprising incombination:

an arbor including means near the ends thereof .for attaching said bitto said string of drill pipe;

21 housing surrounding said arbor in a rotatable sealing relationshiptherewith;

a plurality of ports in the wall of said housing;

thrust units resiliently sealed in said ports, said thrust unitsincluding means for engaging the wall of said borehole and exertingupward force against the borehole wall;

and thrust transfer means between said housing and arbor fortransmitting downward force from said housing to said arbor.

13. Drilling apparatus which comprises:

an arbor section including means located near the ends thereof forrigidly connecting a bit to a drill string and means for conveying fluidfrom the drill string to the bit;

it) and a thrust member se-alingly and resiliently mounted in each ofsaid ports, said thrust member including means for engaging the wall ofthe borehole and exerting an upward force against the borehole wall. 14.Apparatus for use in drilling a borehole with a rotary bit whichcomprises in combination:

an arbor section connectable to said bit;

a housing member surrounding said arbor section in a sealing rotatingrelationship;

thrust bearing interconnecting said housing member and said arborsection;

a plurality of ports extending through said housing member;

a ram member resiliently sealed in each of said ports, the longitudinalaxis of said ram member extending at an angle above the horizontal planein the range of from about 30 degrees to about 60 degrees;

and conduit valve means Within said arbor section to alternately connectthe inner side of said resiliently sealed ram member with the interiorof said arbor section and with the exterior of said housing as the arborsection is rotated.

15. Apparatus as defined by claim 14 in which the longitudinal axis ofsaid ram member extends at an angle with the horizontal plane of about45 degrees.

a housing member surrounding said arbor section in a sealing, rotatablerelationship therewith, the inner diameter of said housing member beingsufiiciently larger than the outer diameter of said arbor section todefine an annular chamber between said arbor section and housing member;

port means in said arbor section for providing fluid communicationbetween said chamber and the interior of said arbor section;

a plurality of ports in the wall of said housing member;

References (Iited by the Examiner UNITED STATES PATENTS 556,718 3/96Semrner -99 1,166,153 12/ 15 Ridley et al. 175394 2,481,009 9/49 Gill175-94 2,891,769 6/59 Page 175-76 2,919,121 12/59 Ruth 17-576 X2,946,578 7/60 De Smaele 175-76 X 3,088,532 5/63 Kellner 175-2303,105,561 10/63 Kellner a- 175-230 CHARLES E. OCONNELL, PrimaryExaminer.

6. A METHOD FOR DRILLING A BOREHOLE IN THE EARTH WHICH COMPRISES:ROTATING A DRILL BIT AT THE END OF A DRILL STRING IN SAID BOREHOLE WHILECIRCULATING A DRILLING FLUID INTO THE HOLE THROUGH SAID DRILL STRING ANDBIT; APPLYING UPWARD FORCE TO THE BOREHOLE WALL FROM A LIMITED SECTIONOF THE DRILL STRING ABOVE THE BIT IN RESPONSE TO DRILLING FLUID PRESSUREWITHIN SAID DRILL STRING; AND THEREAFTER APPLYING UPWARD FORCE TO THEBOREHOLE WALL AT SUCCESSIVELY LOWER POINTS ON THE WALL AT A RATESUFFICIENT TO MAITAIN A CONTINUOUS AXIAL FORCE ON SAID BIT.